1. Field of the Invention
The invention is related to devices for cleaning storage tanks. In particular, the invention is related to cleaning waste products from storage tanks which have a high percentage of solids therein. In particular the present invention is related to devices for removing sediment and sludge that accumulates in waste storage tanks.
2. Description of the Related Art
The accumulation of sediment and sludge in storage tanks is common throughout the world. Prior to the invention disclosed in U.S. Pat. Nos. 5,138,741, 5,269,041 and 5,335,395, many storage tanks such as oil storage tanks were periodically cleaned by manned crews which manually shoveled out the sludge which had accumulated on the bottom of the tank.
The invention disclosed in the aforementioned patents could be fitted within a common hatch or manhole which are typically 24 inches in diameter. Such 24 inch diameter circular hatches or manholes are commonly used in the great majority of storage tanks.
Some storage tanks have access ports or access pipes which are much smaller than the 24 inch common manhole or circular hatch found in most storage tanks. In particular, certain nuclear waste sites have access ports and access pipes which have a maximum 12 inch diameter access pipe or port and are inaccessible by the sludge and sediment removal apparatus of the prior art without enlarging the diameter of the access port or reducing the dimensions of the sludge removal apparatus to an impractical size. Creating a larger access port for insertion of a sludge removal apparatus is very expensive in such tanks, and it is thus desirable to provide a sludge removal apparatus that will can be inserted into such tanks through existing small diameter access ports.